CHICAGO -- After spending most of his adult life behind bars, 73-year-old Walter Unbehaun decided to rob another bank in hopes of getting caught. He felt more comfortable in prison, court documents allege, and wanted to spend his final years there.

So the balding, gray-haired South Carolina man leaned on a cane as he walked into a bank in suburban Chicago over the weekend and used a novel stickup line: He had just six months to live, so he had nothing left to lose, according to a federal complaint citing his post-arrest interrogation.

Unbehaun also allegedly lifted his coat to show a teller a silver revolver shoved into his waistband.

Investigators say Unbehaun, of Rock Hill, S.C., walked out of the Harris Bank in Niles on Saturday with $4,178 in his pockets. He wore no disguises, so law enforcement quickly tracked him down using surveillance-camera photos of him holding up the bank, the complaint said.

When authorities stopped Unbehaun on Sunday outside a motel room where he was staying, he immediately threw down his cane and surrendered, saying he knew they were there because he robbed a bank the day before, according to the complaint filed in U.S. District Court in Chicago.